wind turbines

3D-printed concrete piles could anchor floating wind turbines to seabed

Printing turbine parts could make offshore wind farms easier to build and manage.

Winds off the coasts of the US could be used to generate more than double the combined electricity capacity of all the nation's electric power plants, according to estimates.

However, building wind turbines offshore is expensive, requiring parts to be shipped at least 30 miles away from a coast.

Engineers at Purdue University have been conducting research on a way to make wind turbine parts out of 3D-printed concrete – a less expensive material that would also allow parts to float to a site from an onshore plant.

"One of the current materials used to manufacture anchors for floating wind turbines is steel," said Pablo Zavattieri, a professor in Purdue's Lyles School of Civil Engineering. "However, finished steel structures are much more expensive than concrete."

Conventional concrete manufacturing methods also require a mould to shape the concrete into the desired structure, which adds to costs and limits the design possibilities. 3D-printing would eliminate the expense of the mould.

The researchers are working in collaboration with RCAM Technologies, a start-up founded to develop concrete additive manufacturing for onshore and offshore wind energy technology. RCAM Technologies has an interest in building 3D-printed concrete structures, including wind turbine towers and anchors.

3D-printed concrete suction pile

Image credit: RCAM

The team is developing a method that would involve integrating a robot arm with a concrete pump to fabricate wind turbine substructures and anchors. The project is a continuation of the team's research on 3D-printing cement-based materials into bio-inspired designs, such as ones that use structures mimicking the ability of an arthropod shell to withstand pressure.

The research also involves scaling up their 3D printing by formulating a special concrete, using a mixture of cement, sand, aggregates and chemical admixtures to control shape stability when the concrete is still in a fresh state. The goal is to understand the feasibility and structural behaviour of 3D-printed concrete produced on a larger scale outside of the laboratory conditions.

"Offshore wind power is a nearly perfect platform for testing 3D printing," said Jeffrey Youngblood, a Purdue professor of materials engineering.

"The idea we have for this project is to scale up some of the bio-inspired design concepts we have proven on a smaller scale with the 3D printing of cement paste and to examine them on a larger scale," said Mohamadreza Moini, a PhD candidate in civil engineering at Purdue.

The researchers will determine how gravity affects the durability of the larger-scale 3D-printed structure. The scaling-up research could also be applied to optimising and reinforcing structures in general.

"Printing geometric patterns within the structure and being able to arrange the filaments through or playing around with distribution of the steel are both possibilities we have considered for optimising and reinforcing the structures," said Jan Olek, Purdue's James H and Carol H Cure Professor of Civil Engineering.

Engineers are increasingly finding innovative uses for 3D-printed concrete. In El Salvador, a project by Texan developers ICON involved using a prototype mobile printer to 3D-print concrete houses to improve the quality of life for slum dwellers there. The printer was designed to have the ability to print a single-storey, 55-75 square metre home in under 24 hours for less than $4,000.

3D-printed concrete houses were also planned for the Dutch city of Eindhoven. 'Project Milestone' involved the 3D-printing of five houses in a wood in the Meerhoven district of the city. The houses were being printed using a nozzle mounted on a large robotic arm, which follows digital designs to create houses layer by layer.

With 3D-printing, a printable cement mixture is extruded in thin ribbons. This approach to construction allows for waste to be minimised as no excess cement is poured out, as is the case when using moulds.

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